Reproduction steps:
1. Import the provided custom package "New.unitypackage"
2. In the Project window under "Shaders/Breathing" open "breathingGuide01" in Shader Graph
3. Maximize the Shader Graph window and scale the Main Preview

Expected result: Shader Preview scales with the Main Preview window
Actual result: Shader Preview doesn't scale with the Main Preview window and becomes blurry

Reproduces on: Shader Graph 7.1.1 (2019.3.0b5), Shader Graph 7.3.1 (2019.3.9f1), Shader Graph 8.0.1 (2020.1.0b5, 2020.2.0a7)
Could not test on 2018.4.20f1 and 2019.3.0b4 (Shader Graph 7.0.1) due to imported Shader Graph console errors
Could not test on 2017.4.39f1 (No package)